The present invention relates to decontamination formulations and more particularly to formulations for decontaminating surfaces and/or materials contaminated with chemical and/or biological warfare agents and/or nuclear radioactive particles.
Chemical (CW) and biological (BW) warfare agents (collectively CB agents) are becoming an increasingly important part of defence weaponry. Further, radioactive fallout or dusts have also been of concern, since nuclear devices have been added to military arsenals.
Nuclear/Radioactive Particles
Nuclear or radioactive particles pose a significant threat to personnel due to the effects of ionizing radiation. In addition to the initial release of radiation from a nuclear device and radiation caused by emission from materials which have become radioactive as a result of the initial detonation, inhalation of radioactive dusts or particulate matter can lead to significant numbers of casualties long after the attack. As with BW agents, secondary aerosolization poses an ever-present threat and results in the need to wear protective masks for extended periods of time.
Biological Warfare (BW) Agents
BW agents are characterized as microorganisms including bacteria, viruses and fungi. They are particulate in nature and present a significant hazard long after an attack through formation of secondary aerosols which are inhaled. Unlike CW, BW agents may not result in immediate effects. A lapse of hours, days or weeks may occur before the full extent of their effects become apparent. In the case of certain BW agents, like anthrax, spore production ensures that the BW agent can remain in the environment for years while retaining biological activity. While BW agents may be readily removed from a surface they are often merely repositioned in the underlying environment and remain hazardous if disturbed.
Chemical Warfare (CW) Agents
Three main types of persistent and semi-persistent CW agents exist. They are vesicants and two families of nerve gases, V and G, as outlined in Table I.
Vesicants act as blistering agents that attack skin and mucous membranes and are lethal at high doses.
The V agents are in the phosphorylthiocholine class of compounds, while the G agents are phosphonofluoridates. Both share the same reaction chemistry as organophosphorous esters and pesticides. Nerve agents act on the central nervous system by reacting with the enzyme acetylcholinesterase to cause respiratory collapse, convulsions and death.
G-agents tend to be semi-volatile and toxic by inhalation and percutaneous absorption, while V-agents are relatively non-volatile, persistent, and very toxic by the percutaneous route.
The threat of the use of CB agents and nuclear devices has prompted the need to develop protective and decontamination measures for personnel and military hardware.
Decontaminationxe2x80x94Radioactive Particles
As radioactive particles are nuclear in origin, decontamination cannot deactivate the radioactive hazard. However, the removal of the particulate matter from equipment can significantly reduce aerosolization potential and the spread of the radioactive hazard to clean areas. Generally, removal of the particulate matter requires the encapsulation of the particles and subsequent removal of the encapsulated material from equipment surfaces.
Decontaminationxe2x80x94BW Agents
In the case of BW agents, personal protective equipment such as masks, protective suits etc. are the primary defence against contamination. In some cases, where time and environmental conditions exist, natural weathering such as exposure to sunshine, heat and moisture may destroy the BW agent.
For many BW agents, standard disinfectants can be very effective as decontaminants. An example is the use of hypochlorites or chlorine gas in the treatment of water supplies, swimming pools and in sanitizing food preparation equipment. Active chlorine is considered to be among the most economical yet most effective broad spectrum BW agent decontaminant. Hypochlorites have been shown to be effective against some of the most robust BW agents such as anthrax spores as well as viruses and bacteria. Hypochlorous acid is superior to that of hypochlorite anion as it more readily crosses the cell membrane. Thus, it would be advantageous to perform decontamination of BW agents in a slightly acidic, neutral or slightly basic media where hypochlorous acid is a dominant active component rather than in a strongly basic solution, where hypochlorite anion is the predominant species.
Decontaminationxe2x80x94CW Agents
CW agent decontamination presents a number of challenges. Following a CW agent attack, the semi-persistent or persistent nature of these agents allows them to remain toxic, not only during dissemination, but also for many hours or even days after the attack. The principal hazard occurs through direct inhalation of the vapor off-gassed from the agent or through physical contact with the skin or mucous membranes, through which it is absorbed.
Generally
Ideally, a decontamination formulation should be broad-spectrum in nature, as in most cases the actual nature of the warfare agents being faced is not known. It should be compatible with, and non-corrosive to, equipment used in its application as well as to the equipment to be decontaminated. It should not soften nor damage paints, coatings, polymeric seals or gaskets or transparencies such as windscreens. It should not interfere with in-service monitoring equipment used to verify the effectiveness of the decontamination or to locate residual contamination. It should be easy to prepare, easy to apply and remove, and remain stable for reasonable lengths of time after preparation. It is highly desirable that it adhere to and coat vertical surfaces for sufficient periods of time for agent desorption from the surface and detoxification, yet be easy to remove by evaporation or by rinsing. If used in combination with a surfactant, the decontamination formulation should not compromise the integrity of the foam. It should be of low toxicity, be non-flammable and have a low impact on the environment in order that training can be realistically and frequently performed. Preferably, the formulation should be based in media capable of solubilizing and supporting detoxification of the sparingly soluble CW agents and solubilizing and degrading polymeric thickeners in which the CW agent may reside. Often, these thickeners have high adherence to surfaces and are more difficult to remove than the agents in neat form. Where possible, the decontaminant should be in a concentrated form for mixing with water or other suitable diluent in order to reduce logistical loads on transport and storage and should be readily mixed. For economic reasons it should be formulated from compounds that are readily available in large quantities and be stable in storage for long periods of time. Ideally, the media for dilution should be water or seawater as, in most cases, it is readily available on site and is non-toxic.
Prior art decontamination formulations have taken advantage of the fact that CW agents can generally be oxidized or hydrolyzed, dependent upon their structure, to result in non-toxic products. Many BW agents are readily decontaminated by those same active ingredients, such as hypochlorite and radioactive particles are encapsulated by the surfactants utilized to cause the formulations to adhere to vertical surfaces and are removed and diluted during the removal of the formulation, generally by washing.
In the case of V agents, mustards and biological warfare agents, oxidation has been most successful. Various reactants such as hypochlorites, permanganates, N-chloro and N-bromo compounds, ozonizing compounds and peroxides have been used.
G-agents are not easily oxidized, therefore hydrolysis is normally utilized to address this family of agents. Although hydrolysis can be effective with mustards, they must be in solution before they can be hydrolyzed. Hydrolysis can be accomplished using hydroxides or hypochlorites acting as catalyst, and by water, often with the addition of metal salts to catalyze the reaction. Hydrolysis utilizing enzymes such as organophosphorus acid anhydrase has been studied, although large scale broad spectrum decontaminants are not yet available using this approach.
Nucleophilic displacement can be used to decontaminate nerve and vesicant agents. Since it involves replacement of one group with another less active one, the processes of oxidation and hydrolysis are not necessarily employed. In order to be effective, a formulation utilizing nucleophilic displacement must provide stoichiometric replacement species for all of the CW agents it may encounter, thus adding to the logistical load of transport and storage.
Among the first decontaminants to be used was bleach powder and, to a much lesser degree, potassium permanganate. Bleach can convert CW agents into inert products at the liquid (Bleach solution) or liquid-solid (bleach powder) interface within a few minutes via vigorous oxidation and elimination reactions. However, there are disadvantages. The active chlorine content in bleach decreases gradually with storage time, hence an excess amount of bleach is needed for the oxidation of some agents. In addition, its alkalinity can be corrosive to metal surfaces. Its effectiveness is limited to removing agents from surfaces, since it is not effective in removing agents that have already penetrated into paints.
Following the use of bleach as a decontaminant, the US Army introduced Decontamination Solution 2 (DS2), which is a wide-spectrum, ready-to-use, chemically reactive nucleophilic decontaminant, having long-term stability over an extended range of temperature of xe2x88x9226xc2x0 C. to 52xc2x0 C. This polar non-aqueous liquid consists, by weight, of 70% diethylenetriamine, 28% ethylene glycol monomethyl ether and 2% sodium hydroxide. At ambient temperature, it reacts with any of the HD, VX, GA or GB agents within a few seconds. Typically, DS2 is premixed and stored in 1.3 qt cans, 5-gallon pails and 14-L containers.
However, DS2 does have drawbacks. It is a highly aggressive chemical solution that is toxic and flammable. It damages paint, plastics, rubber and leather materials and, in use, leads to rapid corrosion and oxidation of some metals. It must be used in its premixed form, which poses a logistical transport problem. DS2 is corrosive to the skin, requiring personnel handling it to wear respirators with eye shields and chemically protective gloves to avoid skin contact. Ethylene glycol monomethyl ether has been identified as being toxic to personnel.
Another popular decontaminant is the German Emulsion (C8) system. This system consists, by weight, of 76% water, 15% perchloroethylene, 1% anionic surfactant and 8% high-test-hypochlorite (HTH). Many of the benefits of this system are attributed to the perchloroethylene continuous phase. C8 is of low corrosivity despite the high pH of the aqueous phase. It is effective in dissolving thickeners and can penetrate paint and react with the embedded agents, without damaging the paint. It is viscous enough to provide a thin and coherent film on the surface to allow sufficient time for reaction with the agents.
C8 has several drawbacks. It must be mixed for periods of up to an hour prior to use to generate the emulsion. Even then, it is possible that no emulsion will form. Perchloroethylene has recently been identified by the Canadian and other governments as being environmentally unacceptable and its production and use has been discouraged. The eventual goal is to completely phase out its production. Removal of the perchloroethylene from the decontaminant would render it incapable of solubilizing thickened agents and dissolving highly insoluble CW agents. The surfactant designed to form the emulsion is difficult to obtain. It was originally only available from a manufacturer in West Germany, which has recently discontinued its production.
Clearly, given the drawbacks of the existing decontamination formulations, it is necessary to develop a formulation that is stable, non-toxic to personnel and to the environment, of low corrosivity, effective against a broad spectrum of CW agents, BW agents, and, optionally, radioactive particulate matter, prepared on site in a substantially aqueous medium and capable of coating surfaces, including vertical surfaces, for a minimum of 30 minutes as outlined by NATO.
It is clear that the effectiveness of any formulation does not rely solely on the active ingredient, but rather with its overall composition.
A decontamination formulation is provided which is effective against a broad spectrum of chemical and biological warfare agents, including those with persistent spore production. Further, it is capable of encapsulating particulate radioactive material for facilitating efficient removal by scrubbing and/or rinsing.
In a simplified aspect of the present invention, the decontamination formulation comprises a synergistic combination of an active decontamination agent, a co-solvent preferably undetectable by decontamination monitoring equipment which aids in solubilization of relatively insoluble chemical warfare agents and thickened agents, a buffer system to optimize the initial reaction pH above 8.5 and more preferably in the range of 10 to 11 for favoring oxidation of VX and HD and hydrolysis of G agents, and finally a surfactant to aid in encapsulation of particulate matter and formation of a reliable foam of uniform bubble size when aerated. The surfactant enables foaming of the formulation for coating of surfaces including adherence to vertical surfaces. This coating is stable for sufficient time to ensure effective contact and decontamination. The formulation of the present invention is soluble in an aqueous medium and the use of gray or seawater does not significantly affect its activity.
By varying the concentration of active ingredients within the formulation, a family of formulations result which are capable of responding to different hazardous situations. For rapid decontamination of surfaces, thin layers of foam may be sufficient, but strong active ingredient formulations are required. On the other hand, thick, uniform bubble size foam is an effective blast suppressant. High contamination is best handled with strong active ingredient formulations but the foam""s structure, an important property for blast suppression, can be somewhat compromised by high amounts of added ingredients, such as decontaminants. At reduced amounts of active decontaminant, the foam""s structure remains unaltered, allowing it to be used for blast suppression, yet retain decontamination abilities. Further, reducing active decontaminant and buffer strength may also result in decreased corrosivity.
Accordingly, in a broad aspect of the present invention, there is provided a family of decontaminant formulations comprising:
from about 1% to about 15% by weight and preferably from about 3% to about 9% by weight of a hydrated chloroisocyanuric acid;
from about 1% to about 10% and preferably from about 8% to about 10% by volume of a co-solvent selected from the group consisting of polypropylene glycols, polyethylene glycols, and derivatives and mixtures thereof;
from about 1% to about 15% and preferably from about 1% to about 10% by volume of a surfactant;
a buffer system to initially maintain said formulation at a pH from about 8.5 to about 11 for a minimum of 30 minutes and preferably initially, from about 10 to about 11; and
the balance being water.
Preferably, the chloroisocyanuric acid is selected from the group consisting of an alkali metal of monochloroisocyanuric acid and dichloroisocyanuric acid such as sodium dichloroisocyanurate, trichloroisocyanuric acid and a combination thereof with cyanuric acid. The formulation may additionally comprise lithium hypochlorite to enhance the activity of the dichloroisocyanuric acid salt.
In one preferred embodiment of the invention, the polypropylene glycol has the chemical formula R1xe2x80x94(OCH(CH3)CH2)nxe2x80x94OR2, where R1 and R2 are independently H, an alkyl, or an ester group and n greater than 1 or alternately, a partially etherified polypropylene glycol where one of R1 and R2 is independently H, or an alkyl group and n greater than 1. In both cases the alkyl group may consist of a methyl, ethyl, propyl, butyl or a mixture thereof. Use of certain higher molecular weight co-solvents avoids subsequent false positive detection of the co-solvent as residual contaminant by some monitoring equipment.
Preferably, the buffer system forming the decontamination formulation is a dual component inorganic buffer mixture of sodium tetraborate decahydrate and anhydrous sodium carbonate adjusted to an initial pH of from about 10 to about 11 using sodium hydroxide or, optionally, sodium metasilicate pentahydrate.
One suitable surfactant consists of a composition of the formula [R(OCH2CH2)nX]aMb, where R is an alkyl group having from eight to eighteen carbon atoms; n is an integer from 0 to 10; X is selected from the group of SO32xe2x88x92, SO42xe2x88x92, CO32xe2x88x92 and PO43xe2x88x92, M is an alkali metal, alkaline earth metal, ammonium or amine derivative; a is the valence of M and b is the valence of [R(OCH2CH2)nX] or a mixture thereof.
Preferably, the surfactant consists of a composition of the formula [Rxe2x80x94CHxe2x95x90CH(CH2)mxe2x88x92X]aMb where R is an alkyl group having from eight to eighteen carbon atoms; m is an integer from 0 to 3; X is selected from the group of SO32xe2x88x92, SO42xe2x88x92, CO32xe2x88x92 and PO43xe2x88x92, M is an alkali metal, alkaline earth metal, ammonium or amine derivative; a is the valence of M and b is the valence of [Rxe2x80x94CHxe2x95x90CH(CH2)mxe2x80x94X] or a mixture thereof.
Preferably, the surfactant also consists of a composition of the formulae Rxe2x80x94OH, where R is an alkyl group having from eight to sixteen carbon atoms or mixtures thereof.
Preferably, the surfactant also consists of polypropylene glycol having the chemical formula R1xe2x80x94(OCH(CH3)CH2)nxe2x80x94OR2, where R1 and R2 are independently H, an alkyl, or an ester group and n greater than 1 or alternately, a partially etherified polypropylene glycol where one of R1 or R2 is independently H, or an alkyl group and n greater than 1.
In another broad aspect of the present invention there is provided a method of preparing and delivering a decontamination formulation comprising the steps of:
preparing a first aqueous solution comprising about 30% by weight of chloroisocyanuric acid salt or the equivalent active chlorine content of a mixture of chloroisocyanuric salt and lithium hypochlorite;
preparing a second aqueous solution comprising a mixture of sodium tetraborate decahydrate, anhydrous sodium carbonate, adjusted to a pH of from about 10 to about 11;
providing a co-solvent selected from the group consisting of polypropylene glycol, polyethylene glycol and a derivative and mixture thereof;
providing a surfactant comprising a composition of the formulae [R(OCH2CH2)nX]aMb, where R is an alkyl group having from eight to eighteen carbon atoms; n is an integer from 0 to 10; X is selected from the group of SO32xe2x88x92, SO42xe2x88x92, CO32xe2x88x92 and PO43xe2x88x92, M is an alkali metal, alkaline earth metal, ammonium or amine derivative; a is the valence of M and b is the valence of [R(OCH2CH2)nX] or a mixture thereof;
preferably, a composition of the formula [Rxe2x80x94CHxe2x95x90CH(CH2)mxe2x80x94X]aMb where R is an alkyl group having from eight to eighteen carbon atoms; m is an integer from 0 to 3; X is selected from the group of SO32xe2x88x92, SO42xe2x88x92, CO32xe2x88x92 and PO43xe2x88x92, M is an alkali metal, alkaline earth metal, ammonium or amine derivatives; a is the valence of M and b is the valence of [Rxe2x80x94CHxe2x95x90CH(CH2)mxe2x80x94X] or a mixture thereof;
preferably, the surfactant also consists of a composition of the formulae Rxe2x80x94OH, where R is an alkyl group having from eight to sixteen carbon atoms or mixtures thereof;
preferably, the surfactant also consists of polypropylene glycol having the chemical formula R1xe2x80x94(OCH(CH3)CH2)nxe2x80x94OR2, where R1 and R2 are independently H, an alkyl, or an ester group and n greater than 1 or alternately, a partially etherified polypropylene glycol where one of R1 or R2 is independently H, or an alkyl group and n greater than 1;
providing source water; and
pumping the formulation through an aeration nozzle to create a decontamination foam.
In a preferred aspect of the present invention, the co-solvent and surfactant are mixed together and pumped with the source water through a pumping device. The first and second aqueous solutions are introduced into the stream between the pump and the aeration nozzle for delivery as a foam. Addition of the more erosive and corrosive active decontaminant and buffer to the stream after the pump is advantageous as it prolongs pump life.
Alternatively, all of the ingredients may be premixed with source water and pumped simultaneously through the pumping device and the aeration nozzle, or may be introduced to the source water stream individually.